1. Field of the Invention
This invention relates to a shock absorbing frame assembly for a bicycle, more particularly to a shock absorbing frame assembly which provides a shock absorbing effect by virtue of a twist of an elongated twistable member about a twisting axis.
2. Description of the Related Art
A conventional shock absorbing frame assembly for a bicycle generally includes a hydraulic (or pneumatic) cylinder (or piston) and a spring associated with the cylinder to absorb the shock generated as a result of running of a rear wheel of the bicycle on an uneven or bumpy road.
The shock absorbing effect that is provided by the conventional shock absorbing frame assembly is influenced by the length of a cylinder arm for travel of the cylinder. Specifically, a relatively long cylinder arm can provide a sufficient shock absorbing effect. However, the spring employed therein must possess a relatively large rigidity, which will undesirably reduce the shock absorbing effect. On the other hand, a relatively short cylinder arm results in a poor shock absorbing effect. Moreover, the arrangement of the cylinder and the spring on the bicycle mars the appearance of the bicycle as a whole.
The object of the present invention is to provide a shock absorbing frame assembly which is capable of providing an excellent shock absorbing effect, and which can enhance the aesthetic appeal of the frame assembly.
According to this invention, the shock absorbing frame assembly includes a front frame unit which has a head tube extending in an upright direction, a fork extending downwardly from the head tube, and adapted for mounting of a front wheel to permit rotation of the front wheel relative thereto about a front axis, and a down tube extending downwardly and rearwardly from the head tube and terminating at a bottom end. A seat mount is disposed opposite to the bottom end of the down tube in the upright direction. A rear frame unit includes a seat stay which has an upper coupling end coupled relative to the seat mount, and an intermediate segment extending from the upper coupling end rearwardly and downwardly and terminating at a rear mount end that is adapted for mounting of a rear wheel to permit rotation of the rear wheel relative thereto about a rear axis parallel to the front axis, and a chain stay which extends forwardly from the rear mount end and which terminates at a lower coupling end. A coupling mount is disposed on and extends downwardly from the down tube, and has a first gripping member which includes first front and rear jaw walls. The first front and rear jaw walls are spaced apart from each other along a first line which is radial to and which is equally divided by a first centerline that is parallel to the front axis. A linking unit includes an anchoring end secured to the lower coupling end, a middle arm extending forwardly from the anchoring end, and a second gripping member which extends forwardly from the middle arm and which is spaced apart from the first gripping member along the first centerline. The second gripping member has second front and rear jaw walls spaced apart from each other along a second line which is radial to and which is bisected by a second centerline that is parallel to the front axis. The first and second centerlines are aligned with each other on a twisting axis. When the chain stay moves angularly relative to the front frame unit due to shock generated as a result of running of the rear wheel on an uneven or bumpy road, the second gripping member is caused to turn from a normal position, where the first and second lines are in a same normal plane, to a strained position, where one of the first and second lines is out of the normal plane. An elongated twistable member extends along the twisting axis, and includes left and right gripped regions opposite to each other and in frictional engagement with the first and second gripping members, respectively, so as to prevent angular movements of the left and right gripped regions relative thereto, respectively, when the second gripping member is turned between the normal and strained positions, and an intermediate segment made of a material, which is twistable about the twisting axis to permit the second gripping member to turn to the strained position, so as to acquire a biasing force for urging the second gripping member to turn to the normal position, thereby counteracting the force of the shock. A bearing member is disposed to hold the intermediate segment on the twisting axis when the second gripping member is turned between the normal and strained positions.